Various optical systems require a reflective mirror for changing the direction of a beam of visible or invisible electromagnetic radiation. In order to accomplish this task, the mirror must be rotatable about two mutually perpendicular axes. Such a function may be provided by a gimballed mirror assembly.
By way of example, one use for the present invention is the field of laser radar (LADAR) systems wherein, due to space restraints, a generated laser beam is reflected off of mirrors to emerge at an exit port. A return beam is also changed in direction to impinge upon a receiver system. In such an environment the gimballed mirror assembly must be lightweight and must perform in the presence of extreme vibration.
Some typical gimballed mirror assemblies utilize bulky and heavy components and require springs to apply pressure on adjusting mechanisms. Although satisfactory for laboratory use, this method of providing positive contact permits vibratory responses to enter the assembly thereby rendering it essentially inoperative for use in aircraft.
The present invention obviates the drawbacks of present day gimballed mirror assemblies by providing a gimballed mirror assembly which is not only lightweight, but also which eliminates the requirement for any adjusting springs.
A gimballed mirror assembly in accordance with the present invention includes a housing with an outer gimbal unit positioned within the housing. A pair of ball bearings respectively positioned on opposite sides of the outer gimbal unit between the housing and the outer gimbal unit permits rotation of the outer gimbal unit about an axis passing through the ball bearings. An inner gimbal unit is positioned within the outer gimbal unit and another pair of ball bearings respectively positioned on the top and bottom of the inner gimbal unit between the outer gimbal unit and the inner gimbal unit permits rotation of the inner gimbal unit about an axis passing through the other pair of ball bearings. Preferably the ball bearings seat in conical depressions formed in the various components.
A first pair of adjusting screw assemblies are mounted to contact and position the inner gimbal unit and to maintain it in a selected position, and a second pair of adjusting screw assemblies are mounted to contact and position the outer gimbal unit and to maintain it in its selected position. Completing the assembly is a mirror having a reflective surface and carried by the inner gimbal unit.